The doctrine of “Mahdism” is one of the most prominent ideas in the positive and negative attitudes of Islamic sects. After the minor occultation, the absence of the present Imam and the projection of the controversial questions about the absent Imam and the newly appeared ideals against the Imamates view caused the Imamates scholars, like Sheikh Tusi, to seek to answer these doubts. The present paper, with the descriptive-analytic method, has investigated Sheikh Tusi’s method in responding to the Mahdism doubts in the book “Al-Ghaybah”. The analysis of method of Sheikh prepares new grounds in deepening Mahdavi researches in addition to presenting appropriate models in accordance to the present era in answering the Mahdism doubts. Based on the findings of this paper, Sheikh Tusi’s approach to answering the doubts of various sects has profited consensus, rational reasons, the study of narrators, the contextual study of hadith, and Muslim theology in addition to the usages of the narrations. In addition to rational reasons, he has used history and the Qur’an’s verses and narrations in the supposed doubts.